1. Field of the Invention
This invention relates to the production of antibodies specific to chicken major histocompatibility complex class I molecules for the determination of chicken haplotype.
2. Description of the Prior Art
The chicken major histocompatibility complex (MHC) haplotype of chickens is intimately associated with resistance or susceptibility to viral diseases (Briles et al., 1977, Science, 195:193). Because of its strong association with disease resistance, the determination of the MHC haplotype has been of great interest to poultry breeders seeking to improve flocks (Bacon, 1987, Poultry Sci., 65:802-811).
The chicken MHC (B-complex) is comprised of three classes of highly polymorphic loci, class I (B-F), class II (B-L), and class IV (B-G). See FIG. 1. Six class I loci have been identified scattered throughout the chicken MHC (Guillemot et al., 1988, EMBO J., 7:2775) and there is evidence that more than one locus is expressed at the RNA level (Crone et al., 1985, Immunogenetics, 21:181, and Hunt and Sturgeon, 1993, Poultry Sci., vol. 72 suppl. pp 102). Recent evidence suggests that chicken class I sequences are located on two different chromosomes, or on a microchromosome containing a high frequency of recombination (Miller et al., 1994, P.N.A.S. USA, 91:4397).
The chicken MHC class I glycoproteins are biochemically and functionally similar to the mammalian class I molecules (Plachy et al., 1992, Crit. Rev. Immunol., 12:47). These 40-42 kd molecules are expressed on virtually all cells and are thought to play a central role in MHC restricted antigen presentation to cytotoxic T-cells (Maccubin and Schierman, 1986, J. Immunol., 136:12, and Weinstock et al., 1989, Eur. J. Immunol., 19:267). Recently, sequences from several alleles of the BFIV (class I) locus have been determined from both genomic libraries and cDNA (Hunt et al., 1994, Immunogenetics, 40:370-375, Kaufman et al., 1992, J. Immunol., 148:1532-1546, Kroemer et al., 1990, Immunogenetics, 31:405-409, and Pharr et al., 1994, Eur. J. Immunogenet., 21:59-66).
Traditionally the chicken MHC haplotypes have been defined using alloantisera in a hemagglutination assay. At least twenty seven different B haplotypes have been defined in chickens (Briles and Briles, 1982, Immunogenetics, 15:449-459, and Briles et al., 1982, Immunogenetics, 15:441-447). However, haplotype determination can be very complex as alloantisera show extensive cross-reactivity (Briles and Briles). The presence of immunogenic B-G (class IV) molecules, shared alleles between haplotypes, or antigenic epitopes found in more than one allele may all contribute to this cross-reactivity.